GENERAL BOTANY 



SECTION 1 

 MORPHOLOGY 



Tin; object of vegetable morphology is the scientific study of the 

 forms of plants. It does not attempt to discover the causes of the 

 variation in the forms, but rather has accomplished its purpose when 

 it succeeds in showing how one form may be derived from another. 

 The only real basis of morphological study is, accordingly, the genea- 

 logical development or phylogeny (p. 2). As phylogenetic develop- 

 ment can only be inferred, and cannot be directly followed, the 

 methods of morphology must also be indirect. They are dependent 

 on the one hand upon ontogeny, i.e. on the study of the development 

 passed through by an organism in attaining its mature condition, 

 and on the other hand upon the comparison of existing organisms 

 with one another and with those that have become extinct. To a 

 certain extent the ontogenetic development of a plant repeats its 

 phylogeny and helps to elucidate the latter, while, by means of com- 

 parative investigation, extreme forms may be connected by inter- 

 mediate links. As, however, the ontogeny of a plant is neither a 

 complete nor invariable repetition of its phylogeny, and as connecting 

 links between extreme forms are often wanting, the results of 

 morphological study are frequently incomplete. Such parts or members 

 of plants which it is reasonable to presume have had a common 

 origin are distinguished as HOMOLOGOUS ; those which, while probably 

 having different origins, yet exercise the same functions, are termed 

 ANALOGOUS. Through the adaptation of different parts to the same 

 function, a similarity in both external form and internal structure 

 often results ; and in this way the correct determination of morpho- 

 logical relationships is rendered difficult. Only homologous parts 

 have the same " morphological value." This homology is determined 



